1. Field of the Invention
This invention relates to an image processing system and method, and more particularly to such a system including a plurality of image processing devices having different resolutions.
2. Background Art
Recently, image processing devices such as facsimiles have come into wide use, and their processing environment advances from a local one to a systematic one.
Differing from coded data, image data has no meaning by itself, but has meaning when it is developed on a two-dimensional plane. Thus, the image depends on parameters defining the plane such as the numbers of vertical and horizontal pels, gray levels, and so on, which usually differ from device to device. This leads to problems of various resolution, compression/decompression and image data transmission.
Input/output devices for images (scanners, printers, displays, and so on) being currently manufactured have various resolutions, but it is difficult to interconnect the devices having different resolutions. A problem of how to perform conversion of the different resolutions may because it may be desirable to store image data with different resolutions would be stored in a common image data base in the future.
At present, there are methods of compression of image data such as the Modified Huffman and the Modified READ, which define their codes (or compression conversions) based on the statistics of image data having a predetermined resolution. Therefore, if the resolution differs, optimum coding (compression conversions) cannot be performed.
Generally, the display has a lower resolution than the scanner. When it is intended to display an image scanned by the scanner on the display, it is currently generally accomplished in such a manner that high resolution image data is transferred to the display in its entirety, where it is converted to low resolution image data. This results in wasteful data transmissions. A more preferable way would be to send only image data that fits the resolution of a receiving device.
These problems relate to expression methods of image data. Conventional methods such as binary, mosaic, DF and run length expressions cannot solve the problems because they do not consider the difference of resolutions.
Arranging image data in a hierarchial or pyramidal manner is well known in the prior art and described, for example, in U.S. Pat. No. 4,222,076 and K. R. Sloan, Jr., S. L. Tanimoto, "Progressive Refinement of Raster Images," IEEE TRANSACTIONS ON COMPUTERS, Vol. c-28, No. 11, November 1979, pp. 871-874. However, the conventional image data structures have been devised with the purpose of retrieving, and the data contents of the respective layers are different from those of the invention. In addition, the hierarchial systems they have a disadvantage that larger storage space is required as compared with only storing the original image data.
Other limitations and disadvantages of prior art systems will be apparent to those skilled in the art in view of the following description of the present invention, taken with the appended claims and the accompanying drawings.